When cleaning combustion gases in a PFBC plant the main objectives are:
1. A sufficiently good cleaning in view of the gas turbine and the surrounding environment.
2. A small pressure vessel surrounding the combustion chamber owing to the pressure and as a result of this a small volume of the cleaning plant in the space between the combustion chamber and the pressure vessel.
3. As small a pressure drop as possible for a high gas turbine effect.
4. As small a loss flow as possible for ash conveyance etc.
5. The lowest possible cost.
6. A sufficient life of the plant in spite of the fact that the cleaning plant is subjected to high thermal stresses because of high temperature of the gas which is to be cleaned.
Because of the large volume, the high cost and the insufficient life, cleaning plants with filters are not used in PFBC plants.
Up to now, cleaning plants of cyclone type have been used in PFBC plants.
The positive properties are:
The separation is sufficiently good for propellent gas to the turbine PA1 There is no loss flow PA1 The cost is moderate PA1 A long life is obtained. PA1 A high pressure drop.
A negative property is:
The problem comprises providing, for a PFBC plant, a cleaning plant which is superior to a cyclone type cleaning.